The ability to control the biochemistry of cells and organisms with light has elicited widespread attention. However, in spite of the promise that optogenetic tools hold for biology and medicine, their ready application is constrained by protein engineering strategies that are labor intensive and require a level of biochemical and cellular engineering sophistication that is not available in many biology labs. Indeed, although much has been made of the potential of optogenetics, surprisingly few genetically encoded light-responsive proteins have been described. Is it possible to devise an optogenetic protein engineering strategy that is so straightforward that biologists can serve as their own protein engineers? In this regard, we have developed a potentially general strategy that draws its inspiration from the 100-year-old Michaelis Menten equation. This approach has furnished a light-activatable cofilin (light-mediated cell motility) and a light-activatable bax (light-mediate cell death). We will prepare three additional light-responsive proteins in order to explore the scope and limitations of this strategy. The three constructs to be acquired, in conjunction with the two developed to date, are representatives of a large family of proteins known to modulate mitochondrial behavior. Several neurological diseases (Parkinson's, Huntington's, Alzheimer's, and Charcot-Marie-Tooth type 2A) display defects in mitochondrial dynamics, including fusion, fission, transport, and turnover. Recent studies have suggested that it may be possible to ameliorate specific disease phenotypes by altering mitochondrial dynamics. We will explore this premise by examining the ability of the light-responsive proteins under study to modulate mitochondrial behavior in a light-dependent fashion.